Multi-channel tape head having asymmetric channel arrays

ABSTRACT

In one general embodiment, a magnetic head comprises an inner module comprising an array of data readers; and first and second outer modules flanking the inner module. The outer modules are identical, each outer module comprising an array of data writers. A number of active data writers in each outer module is less than a number of active data readers in the inner module. For the first outer module, one of the active data writers is aligned with one of the data reader positioned towards a first end of the inner module array in a direction generally parallel to the path of tape travel thereacross. For the second outer module, one of the active data writers is aligned with one of the data readers positioned towards a second end of the inner module array in the direction generally parallel to the path of tape travel thereacross.

RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.12/047,075, filed Mar. 12, 2008, which is herein incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to magnetic head structures, and moreparticularly, this invention relates to a magnetic head structure havingasymmetric channel arrays.

BACKGROUND OF THE INVENTION

Business, science and entertainment applications depend upon computingsystems to process and record data, often with large volumes of the databeing stored or transferred to nonvolatile storage media, such asmagnetic discs, magnetic tape cartridges, optical disk cartridges,floppy diskettes, or floptical diskettes. Typically, magnetic tape isthe most economical and convenient means of storing or archiving thedata. Storage technology is continually pushed to increase storagecapacity and storage reliability. Improvement in data storage densitiesin magnetic storage media, for example, has resulted from improvedmedium materials, improved error correction techniques and decreasedareal bit sizes. The data capacity of half-inch magnetic tape, forexample, is now measured in hundreds of gigabytes on 896 or more datatracks.

SUMMARY OF THE INVENTION

In one general embodiment, a magnetic head comprises an inner modulecomprising an array of data readers; and first and second outer modulesflanking the inner module. The outer modules are identical, each outermodule comprising an array of data writers. A number of active datawriters in each outer module is less than a number of active datareaders in the inner module. For the first outer module, one of theactive data writers is aligned with one of the data reader positionedtowards a first end of the inner module array in a direction generallyparallel to the path of tape travel thereacross. For the second outermodule, one of the active data writers is aligned with one of the datareaders positioned towards a second end of the inner module array in thedirection generally parallel to the path of tape travel thereacross.

A magnetic head according to yet another embodiment comprises an innermodule comprising an array of data writers; and first and second outermodules flanking the inner module. The outer modules are identical, eachouter module comprising an array of data readers. A number of activedata readers in each outer module is less than a number of active datawriters in the inner module. For the first outer module, one of theactive data readers is aligned with one of the data writers positionedtowards a first end of the inner module array in the direction generallyparallel to the path of tape travel thereacross. For the second outermodule, one of the active data readers is aligned with one of the datawriters positioned towards a second end of the inner module array in thedirection generally parallel to the path of tape travel thereacross.

Any of these embodiments may be implemented in a magnetic data storagesystem such as a tape drive system, which may include a magnetic head asrecited above, a drive mechanism for passing a magnetic medium (e.g.,recording tape) over the magnetic head, and a controller electricallycoupled to the magnetic head.

Other aspects, advantages and embodiments of the present invention willbecome apparent from the following detailed description, which, whentaken in conjunction with the drawings, illustrate by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and advantages of the presentinvention, as well as the preferred mode of use, reference should bemade to the following detailed description read in conjunction with theaccompanying drawings.

FIG. 1 is a schematic diagram of a simplified tape drive systemaccording to one embodiment.

FIG. 2 illustrates a flat-lapped bi-directional, two-module magnetictape head which may be implemented in the context of the presentinvention.

FIG. 3 is a partial tape bearing surface view of a magnetic tape headaccording to one embodiment.

FIG. 4 is a representative diagram of an 8-channel, side by side (orinterleaved) magnetic head with two servo readers per module above adiagram of an 8-channel, paired (e.g., piggybacked, merged, or otherwisealigned) symmetric magnetic head with four servo readers per module.

FIG. 5 is a representative diagram of an 8-channel, side by sidemagnetic head with two servo readers per module above a diagram of a16-channel, magnetic head with two servo readers per module.

FIG. 6 is a representative diagram of an 8-channel, side by sidemagnetic head with two servo readers per module above a diagram of a16-channel magnetic head with two servo readers per module above adiagram of a 24-channel merged multiformat magnetic head with two servoreaders per module per format.

FIG. 7 is a representative diagram of an 8-channel, side by sidemagnetic head with two servo readers per module above a diagram of a16-channel magnetic head with two servo readers per module above anembodiment of a 32-channel, backward compatible magnetic head with fourservo readers per module.

FIG. 8 is a representative diagram of an 8-channel, side by sidemagnetic head with two servo readers per module above a diagram of a16-channel magnetic head with two servo readers per module above anembodiment of a 32-channel, asymmetric, backward compatible magnetichead with two servo readers per module.

FIG. 9 is a representative diagram of an 8-channel, side by sidemagnetic head with two servo readers per module above a diagram of a16-channel magnetic head with two servo readers per module above anembodiment of a 32-channel, merged multiformat magnetic head with twoservo readers per module per format.

FIG. 10 is a representative diagram of a magnetic head having multiplemodules according to one embodiment.

FIG. 11 is a representative diagram of a magnetic head having multiplemodules according to another embodiment.

FIG. 12 is a top down view of magnetic head 1002 of FIG. 10.

DETAILED DESCRIPTION

The following description is made for the purpose of illustrating thegeneral principles of the present invention and is not meant to limitthe inventive concepts claimed herein. Further, particular featuresdescribed herein can be used in combination with other describedfeatures in each of the various possible combinations and permutations.

Unless otherwise specifically defined herein, all terms are to be giventheir broadest possible interpretation including meanings implied fromthe specification as well as meanings understood by those skilled in theart and/or as defined in dictionaries, treatises, etc.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” “an” and “the” include pluralreferents unless otherwise specified.

The following description discloses several preferred embodiments oftape-based storage systems, as well as operation and/or component partsthereof.

The embodiments described below disclose a new head design that iscapable of reading and/or writing to magnetic media such as magnetictape in multiple formats. For example, the head can write and/or readdata in both legacy and advanced formats, and in doing so can enablefull backward compatibility with legacy media types. This is animportant criterion for customers wishing to move to a new format yethaving data stored on media in an older format.

This following description also presents solutions to the problem ofdesigning and making a magnetic tape head which is backward compatiblewith prior tape formats, and which can be built from two or moreface-to-face modules two or more of which are generally identical, andhave a minimal set of transducers. In particular, embodiments disclosedbelow provide a solution for such head to have only two servo readersper module and/or per format; whereas previous concepts suggestrequiring a minimum three or more servo readers per format per module.The following description also provides identical module solutions tomerged array heads wherein rotational symmetry may otherwise not existor be broken.

A magnetic head according to one general approach comprises identical,opposing modules. Each module comprises an array of paired datatransducers, the transducers being including data readers, data writers,or combinations thereof. For each array, the transducers in each subsetmay have about the same center to center spacing. A first subset of thetransducers is operable for reading or writing data in a first tapeformat. A second subset of the transducers is operable for reading orwriting data in a second tape format, with at least some of thetransducers being present in both subsets. Also, each module includes alone writer at one end of one of the subsets, a lone reader at anopposite end of the one of the subsets, and servo readers positionedoutside the array. “Identical” as used herein means that the modules aredesigned to have the same transducer layout, and possibly as similar astructure as possible given processing constraints and tolerances.

Another general embodiment comprises a magnetic head which comprisesidentical, opposing modules. Each module comprises an array of datatransducers, the transducers including data readers, data writers, orcombinations thereof. A first subset of the transducers is operable forreading or writing data in a first tape format. A second subset of thetransducers is operable for reading or writing data in a second tapeformat, with at least some of the transducers being present in bothsubsets. Also included are servo readers positioned outside the array.For each module, one of the data transducers is positioned along acenterline of the array.

In another embodiment, a magnetic head comprises identical, opposingmodules. For each module, only one servo reader may be positioned oneach side of the array. Also, for each module, the data transducerpositioned along the centerline of the array may belong to only one ofthe subsets. Further, for each array, the transducers in the firstsubset may have the same center to center spacing as the transducers inthe second subset. Conversely, for each array, the transducers in thefirst subset may have a different center to center spacing than thetransducers in the second subset. In this and other embodiments, amagnetic head may also comprise, for each module, a pair of servoreaders interleaved with the transducers as shown as head 902 in FIG. 9.

In another general approach, a tape drive system comprises a magnetichead comprising identical, opposing modules. Also, a drive mechanism forpassing a magnetic recording tape over the head is included, along witha controller in communication with the head.

In a further general embodiment, a magnetic head comprises an innermodule comprising an array of data readers; and first and second outermodules flanking the inner module. The outer modules are identical, eachouter module comprising an array of data writers. A number of activedata writers in each outer module is less than a number of active datareaders in the inner module. For the first outer module, one of theactive data writers is aligned with one of the data reader positionedtowards a first end of the inner module array in a direction generallyparallel to the path of tape travel thereacross. For the second outermodule, one of the active data writers is aligned with one of the datareaders positioned towards a second end of the inner module array in thedirection generally parallel to the path of tape travel thereacross.

A magnetic head according to yet another embodiment comprises an innermodule comprising an array of data writers; and first and second outermodules flanking the inner module. The outer modules are identical, eachouter module comprising an array of data readers. A number of activedata readers in each outer module is less than a number of active datawriters in the inner module. For the first outer module, one of theactive data readers is aligned with one of the data writers positionedtowards a first end of the inner module array in the direction generallyparallel to the path of tape travel thereacross, For the second outermodule, one of the active data readers is aligned with one of the datawriters positioned towards a second end of the inner module array in thedirection generally parallel to the path of tape travel thereacross.

In another embodiment, the tape drive system is part of a larger libraryof tape drive systems that provide coordinated data backup using severaldrives.

FIG. 1 illustrates a simplified tape drive 100 of a tape-based datastorage system, which may be employed in the context of the presentinvention. While one specific implementation of a tape drive is shown inFIG. 1, it should be noted that the embodiments described herein may beimplemented in the context of any type of tape drive system.

As shown, a tape supply cartridge 120 and a take-up reel 121 areprovided to support a tape 122. One or more of the reels may form partof a removable cassette and are not necessarily part of the system 100.The tape drive, such as that illustrated in FIG. 1, may further includedrive motor(s) to drive the tape supply cartridge 120 and the take-upreel 121 to move the tape 122 over a tape head 126 of any type.

Guides 125 guide the tape 122 across the tape head 126. Such tape head126 is in turn coupled to a controller assembly 128 via a cable 130. Thecontroller 128 typically controls head functions such as servofollowing, writing, reading, etc. The cable 130 may include read/writecircuits to transmit data to the head 126 to be recorded on the tape 122and to receive data read by the head 126 from the tape 122. An actuator132 controls position of the head 126 relative to the tape 122.

An interface may also be provided for communication between the tapedrive and a host (integral or external) to send and receive the data andfor controlling the operation of the tape drive and communicating thestatus of the tape drive to the host, all as will be understood by thoseof skill in the art.

By way of example, FIG. 2 illustrates a flat-lapped bi-directional,two-module magnetic tape head 200 which may be implemented in thecontext of the present invention. As shown, the head includes a pair ofbases 202, each equipped with a module 204, and fixed at a small angle αwith respect to each other. The bases are typically “U-beams” that areadhesively coupled together. Each module 204 includes a substrate 204Aand a closure 204B with a gap 206 comprising readers and/or writerssituated therebetween. In use, a tape 208 is moved over the modules 204along a media (tape) bearing surface 209 in the manner shown for readingand writing data on the tape 208 using the readers and writers. The wrapangle θ of the tape 208 at edges going onto and exiting the flat mediasupport surfaces 209 are usually between ⅛ degree and 4.5 degrees.

The substrates 204A are typically constructed of a wear resistantmaterial, such as a ceramic. The closures 204B are typically made of thesame or similar ceramic as the substrates 204A.

The readers and writers may be arranged in a paired configuration,meaning that pairs of readers and writers are each present on about asame track location relative to a tape. Types of paired configurationsinclude, but are not limited to, piggybacked transducers, mergedtransducers, etc. An illustrative piggybacked configuration comprises a(magnetically inductive) writer transducer on top of (or below) a(magnetically shielded) reader transducer (e.g., a magnetoresistivereader, etc.), wherein the poles of the writer and the shields of thereader are generally separated. An illustrative merged configurationcomprises one reader shield in the same physical layer as one writerpole (hence, “merged”). The readers and writers may also be arranged inan interleaved configuration. Alternatively, each array of channels maybe readers or writers only. Any of these arrays may contain one or moreservo readers.

FIG. 3 shows a partial tape bearing surface (TBS) view of a magnetictape head assembly 310 according to one embodiment having a plurality ofread/write (R/W) pairs in a paired configuration formed on a commonsubstrate 330 and an optional electrically insulative layer 331. Thewriters, exemplified by the write head 312 and the readers, exemplifiedby the read head 314, are aligned parallel to a direction of travel of atape medium thereacross to form a R/W pair, exemplified by the R/W pair311.

Several R/W pairs 311 may be present, such as 8, 16, 32 pairs, etc. TheR/W pairs 311 as shown are linearly aligned in a direction generallyperpendicular to a direction of tape travel thereacross. However, thepairs may also be aligned diagonally, etc. Servo readers 313 arepositioned on the outside of the array of R/W pairs, the function ofwhich is well known.

Generally, the magnetic tape medium moves in either a forward or reversedirection as indicated by arrow 318. The magnetic tape medium and headassembly 310 operate in a transducing relationship in the mannerwell-known in the art. The paired MR head assembly 310 includes twothin-film modules 322 and 324 of generally identical construction.

Modules 322 and 324 are joined together with a space present betweenclosures 325 thereof (partially shown) to form a single physical unit toprovide read-while-write capability by activating the writer of theleading module and reader of the trailing module aligned with the writerof the leading module parallel to the direction of tape travel relativethereto. When a module 322, 324 of a head 310 having paired transducersis constructed, layers are formed in the gap 323 created above anelectrically conductive substrate 330 (partially shown), e.g., of AlTiC,in generally the following order for the R/W pairs 311: an insulatinglayer 331, a first shield 346 typically of an iron alloy such as NiFe(permalloy), CoZrTa or Al—Fe—Si (Sendust), a sensor 340 for sensing adata track on a magnetic medium, a second shield 348 typically of anickel-iron alloy (e.g., 80/20 Permalloy), first and second writer poletips 356, 358, and a coil (not shown).

The first and second writer poles 356, 358 may be fabricated from highmagnetic moment materials such as 45/55 NiFe. Note that these materialsare provided by way of example only, and other materials may be used.Additional layers such as insulation between the shields and/or poletips and an insulation layer surrounding the sensor may be present.Illustrative materials for the insulation include alumina and otheroxides, insulative polymers, etc.

By way of example, FIG. 4 shows a diagram of an 8-channel, side by side(or interleaved) asymmetric magnetic head 402 with two servo readers permodule above a diagram of an 8-channel, paired transducer, symmetricmagnetic head 404 with four servo readers per module. In FIG. 4, Rdenotes a reader, W denotes a writer, P denotes a transducer pair(reader and writer), and S denotes a servo reader. For head 404, the Rand W indicate a reader and writer for each transducer pair. Thenumbering system above and below each reader, writer, servo reader andtransducer pair indicates one example of how to number the readers andwriters. Head 402 is an asymmetric head because the readers and writersdo not line up vertically on the head. However, this configurationallows for two identical modules to be used to construct the head: oneon the top, and one rotated 180° on the bottom. Again, identical in thecontext of the present description means that the modules are designedto have the same transducer layout, and possibly as similar a structureas possible given processing constraints and tolerances.

The symmetric head 404 is constructed of two modules, one for the top,and one for the bottom. In addition to manufacturing advantages ofproducing identical modules as opposed to two unique modules is that ofusing two servo readers per module over using four servo readers permodule. This advantage is a reduced chance of failure due to servoreader failure. A total of four servo readers on head 402 means thathead 402 has a lower chance of failing compared to head 404, which has atotal of eight servo readers. Therefore, through use of less servoreaders per module, there is less chance of head failure in the exampleof head 402. Also, in order to read and write on the proper track, head404 is moved side-to-side to align the servo readers (S) with the servotracks, which would generally be spaced as indicated by the servoreaders on head 402. This slight movement can cause wear on the headresulting in head failure or servo motor failure due to increased useover the lifetime of the system. In addition, this movement requireslarger margins inside the tape drive to provide for the head's extendedmotion. The increased chance of failure and larger margins requirementexist for any head using multiple servo readers per module side and isnot limited to this example.

FIG. 5 is a representative diagram of an 8-channel, side by sideasymmetric magnetic head with two servo readers per module above adiagram of a 16-channel, symmetric magnetic head with paired transducersand two servo readers per module. In FIG. 5, R denotes a reader, Wdenotes a writer, P denotes a transducer pair (reader and writer), and Sdenotes a servo reader. For head 502, the R and W indicate a reader andwriter for each transducer pair. The numbering system above and beloweach reader, writer, servo reader and transducer pair indicates oneexample of how to number the readers and writers.

In this example, head 502 is a 16-channel head that can be constructedof two identical modules, one for the top and one for the bottom.Identical in the context of this example means that the modules aredesigned to have the same transducer layout, and possibly as similar astructure as possible given processing constraints and tolerances. Head502 also has two servo readers per module, which is consistent with head402 which results in fewer head failures due to servo reader failure.

FIG. 6 is a representative diagram of an 8-channel, side by sideasymmetric magnetic head 402 with two servo readers per module above adiagram of a 16-channel, symmetric magnetic head 502 with pairedtransducers and two servo readers per module above a diagram of a24-channel, 8-data band, symmetric merged multiformat magnetic head 602with two servo readers per module per format. In FIG. 6, R denotes areader, W denotes a writer, P denotes a transducer pair (reader andwriter), L denotes a legacy transducer pair, D denotes a dual-usetransducer pair, n denotes a new generation transducer pair, S denotes alegacy servo reader, and s denotes a new generation servo reader. Forheads 502 and 602, the R and W indicate a reader and writer for eachtransducer pair. The numbering system above and below each reader,writer, servo reader and transducer pair indicates one example of how tonumber the readers and writers. An x indicates that there is no activetransducer of this type at this location on the module. Heads 502 and602 have symmetry about the module centerline and head centerline,whereas head 402 is asymmetric. On head 602, channel pitch for the newgeneration readers and writers (N and D) are on a pitch which is threetimes smaller in this 24-channel example than in the 8-channel or16-channel examples (heads 402 and 502, respectively). In this example,head 602 shows a 24-channel head that can be constructed of twoidentical modules, one for the top and one for the bottom that iscapable of reading and writing in 16-, or 24-channel formats. Identicalin the context of this example means that the modules are designed tohave the same transducer layout, and possibly as similar a structure aspossible given processing constraints and tolerances.

FIG. 7 is a representative diagram of an 8-channel, side by sideasymmetric magnetic head 402 with two servo readers per module above adiagram of a 16-channel, symmetric magnetic head 502 with pairedtransducers and two servo readers per module above a 32-channel,backward compatible symmetric magnetic head 702 with paired transducersand four servo readers per module. In FIG. 7, R denotes a reader, Wdenotes a writer, P denotes a transducer pair (reader and writer), and Sdenotes a servo reader. For heads 502 and 702, the R and W indicate areader and writer for each transducer pair. The numbering system aboveand below each reader, writer, servo reader and transducer pairindicates one example of how to number the readers and writers.Typically, servo readers 2 and 3 may be used for 32-channel formatreading and writing, while servo readers 1 and 3 and/or servo readers 2and 4 may be used for 16-channel format reading and writing. In thisembodiment, head 702 may be moved slightly side-to-side to align theservo readers with the servo track indicated on heads 402 and 502 by theservo reader (S) locations. In this way, the readers and writers may bealigned to read and write on the proper track positions. This layout issimilar to head 404 in FIG. 4 except that the servo reader to servoreader distance on head 702 is equal to the paired transducer (P) pitch,while the servo reader to servo reader distance on head 404 in FIG. 4 isone-half the paired transducer (P) pitch. Having the servo reader toservo reader distance equal to the paired transducer (P) pitch allowshead 702 backward compatibility with 16-channel formats rather thancompatibility with the format optimized from the interleaved head.

In another embodiment, a 32-channel magnetic head, similar to that shownin FIG. 7, uses three servo readers per module, resulting in anasymmetric magnetic head capable of backward compatibility with16-channel heads.

FIG. 8 includes a representative diagram of an 8-channel, side by sideasymmetric magnetic head 402 with two servo readers per module above adiagram of a 16-channel, symmetric magnetic head 502 with pairedtransducers and two servo readers per module above an illustrativediagram of a head 802 according to one embodiment. This embodiment is a4-data band, 32-channel, asymmetric, backward compatible magnetic head802 with paired transducers and two servo readers per module. In FIG. 8,R denotes a reader, W denotes a writer, P denotes a transducer pair(reader and writer), and S denotes a servo reader. For heads 502 and802, the R and W indicate a reader and writer for each transducer pair.The numbering system above and below each reader, writer, servo readerand transducer pair indicates one example of how to number the readersand writers.

In this embodiment, head 802 can be constructed of two identical,opposing modules, one for the top and one for the bottom, which can readand write in 16- and 32-channel formats. Identical in the context ofthis embodiment means that the modules are designed to have the sametransducer layout, and possibly as similar a structure as possible givenprocessing constraints and tolerances. On head 802, the end channel oneach module has one reader or writer instead of a transducer pair,depending on the location. As shown, the writer is on the right side ofthe top (“RIGHT”) module, with the reader on the left side of the topmodule. This arrangement can be reversed, with the writer on the leftside of the top module, and the reader on the right side of the topmodule, as long as a corresponding change is made to the bottom (“LEFT”)module. As shown, there are 32 data channels for the new generationreaders/writers, but these are spread across 33 locations on eachmodule, with a transducer pair (P) now on the module centerline.

For each module, a distance between the servo readers could be such thatthe servo readers read servo bands on a tape written in the first formatand servo bands on a tape written in the second format. In theillustrative embodiment shown, only one servo reader is positioned oneach side of a given array. Further, the servo reader to servo readerdistance on head 802 is about the same as in heads 402 and 502, withservo readers 1 and 2 used for both 32-channel and 16-channel formats.An illustrative servo reader spacing is 2858.9 μm, but, of course, willvary from format to format, i.e., may be higher or lower.

Also, the top and bottom modules may be manufactured with a transducerpair (P) on each end, with one transducer pair (P) only operational forone of the writer or reader, and the other transducer pair (P) onlyoperational for the reader or writer, respectively, or othercombinations, as appropriate. This allows for simplified manufacturingsince only one type of transducer design (P) is to be manufactured,instead of three different types (W, R, P).

Head 802 combines the concepts of the interleaved head into use withpresent-day heads by splitting a transducer pair into a singleinterleaved writer and reader pair split to the ends of the array, whilecentering the rest of the array (of an odd number of transducers, forexample) to the centerline of the module. The active transducer count isminimized, including the servo readers, without loss of function, whilealso maintaining symmetric and identical modules in the cases of both2-module and 3-module heads. By having a minimal set of transducers,head complexity and usage is minimized while head manufacturing (i.e.,yield) is maximized. By having identical modules, manufacturingsimplicity is maximized.

FIG. 9 is a representative diagram of an 8-channel, side by sideasymmetric magnetic head 402 with two servo readers per module above adiagram of a 16-channel, symmetric magnetic head 502 with pairedtransducers and two servo readers per module above one illustrativeembodiment 902. This example 902 is of a 32-channel, 8-data band, mergedmultiformat magnetic head 902 having two modules, each module having anarray of transducers. Each array of transducers has a first subset oftransducers (legacy format) and a second subset of transducers (newformat). Each subset of an array has two servo readers associated withit. In FIG. 9, R denotes a reader, W denotes a writer, P denotes atransducer pair (reader and writer), L denotes a legacy transducer pair,D denotes a dual-use transducer pair, n denotes a new generationtransducer pair, S denotes a legacy servo reader, and s denotes a newgeneration servo reader. For head 502, the R and W indicate a reader andwriter for each transducer pair. The numbering system above and beloweach reader, writer, servo reader and transducer pair indicates oneexample of how to number the readers and writers. An x indicates thatthere is no active transducer of this type at this location on themodule.

With continued reference to head 902 of FIG. 9, for each array oftransducers, the transducers in the first subset have a different centerto center spacing than the transducers in the second subset. In thisembodiment, one of the paired data transducers might be positioned alonga centerline of the array. Also, for each module, the paired datatransducer positioned along the centerline of the array belongs to onlyone of the subsets, here the subset associated with the new format.Another possibility is that for each module, a pair of servo readers maybe interleaved with the transducers as shown as head 902 in FIG. 9.

Heads 402 and 502 have symmetry about the module centerline and headcenterline, whereas head 902 is asymmetric. In this embodiment, theheads 402, 502, 902 can be constructed of two identical modules, one forthe top and one for the bottom, which can read and write in 8-, 16- and32-channel formats, respectively. Also, head 902 is backward compatiblewith 16-channel, 4-data band formats, while capable of writing the32-channel new format across 8 data bands. Head 902 has 8 dual-use pairsof transducers (D) with a four times decrease in the channel pitch ofpairs (n) surrounding them (4×8=32 channels). There are 33 datatransducer locations in the new format array, with a single transducerpair (n) split into a single writer (w) and single reader (r) placed atthe ends of the array. In this embodiment, there are a total of 168transducers (84 per module), but other numbers of transducers arepossible.

In other embodiments, such as those shown in FIGS. 10 and 11, a magnetichead can be constructed with three (or more) modules, instead of two.FIG. 12 illustrates a top down view of the magnetic head 1002 of FIG. 10having modules 1202, 1204, 1206 providing a tape bearing surface, andgaps 1208 therebetween.

In a further embodiment, shown in FIG. 10, a WRW head comprises an innermodule (CENTER) comprising an array of data readers R; and first andsecond outer modules (LEFT, RIGHT) flanking the inner module each havingan array of writers W. The outer modules are identical. A number ofactive data writers in each outer module is less than a number of activedata readers in the inner module. For the first outer module, one of theactive data writers is aligned with one of the data readers positionedtowards a first end of the inner module array in the direction generallyparallel to the path of tape travel thereacross. The data reader may beat the end of the array. Alternatively, the data reader may be at theend of an embedded array (as in arrays in a multiformat embodimentsimilar to that shown in FIG. 9) rather than at the end of the array.For the second outer module, one of the active data writers is alignedwith one of the data readers positioned towards a second end of theinner module array in the direction generally parallel to the path oftape travel thereacross. In the illustrative embodiment shown, each ofthe modules has only two server readers and a transducer on thecenterline, as indicated by W32-R-W33 surrounded by solid lines in themiddle of the modules. The outer modules have asymmetric layouts aboutthis centerline in such a way that the outer modules include only 32read transducers. The inner module is symmetric about its centerline,but is not identical to the outer modules. The inner module includes 33write transducers, but only two servo readers (or optionally one or noservo readers). This allows the WRW head to be comprised of only twodistinct types of modules, one type for the outer write modules, and onefor the inner read module.

In another embodiment, shown in FIG. 11, a RWR magnetic head comprisesan inner module (CENTER) comprising an array of data writers; and firstand second outer modules (RIGHT, LEFT) flanking the inner module. Theouter modules are identical, each outer module comprising an array ofdata readers. A number of active data readers in each outer module isless than a number of active data writers in the inner module. For thefirst outer module, one of the active data readers is aligned with oneof the data writers at a first end of the inner module array in thedirection generally parallel to the path of tape travel thereacross, Thedata writer may be at the end of the array. Alternatively, the datawriter may be at the end of an embedded array (as in arrays in amultiformat embodiment similar to that shown in FIG. 9) rather than atthe end of the array. For the second outer module, one of the activedata readers is aligned with one of the data writers positioned towardsa second end of the inner module array in the direction generallyparallel to the path of tape travel thereacross. In the illustrativeembodiment shown, each of the modules may have only two server readersand a transducer on the centerline, as indicated by R33-W-R32 surroundedby solid lines in the middle of the modules. The outer modules haveasymmetric layouts about this centerline in such a way that the outermodules include only 32 read transducers. The inner module is symmetricabout its centerline, but is not identical to the outer modules,including 33 write transducers, but still only two servo readers (oroptionally one or no servo readers). This allows the RWR head to becomprised of only two distinct types of modules, one type for the outerread modules, and one for the inner write module.

In another approach, the top and bottom modules may be as shown in head802 except that only 32 of the locations may be used (either 1-32 or2-33, leaving the first or last location open), thus eliminating areader or writer from the opposite end of each module. In addition, thecenter module (not shown) may have a complete set of 33 transducers,meaning that the end channels may be a transducer pair (P) on each side,rather than splitting the transducer pair as in the top and bottommodules. This may result in a reader-writer-reader (RWR) orwriter-reader-writer (WRW) on each channel on the head. Also, the topand bottom modules may be manufactured with a transducer pair (P) oneach end, with one transducer pair (P) not connected or operational, andthe other transducer pair (P) only operational for one of the reader orwriter, as appropriate. This allows for simplified manufacturing sinceonly one type of module is to be manufactured, instead of threedifferent types.

Again, as alluded to above, the embodiments of FIG. 10 or 11 mayincorporate a multiformat design as in FIGS. 6-9, with appropriatemodifications of course. For instance, an embodiment of FIG. 10 havingouter modules each with a multiformat array of writers W at positionssimilar to those of FIG. 9, with or without paired transducers at eachlocation, preferably without. Similarly, the inner module of such anembodiment may have readers R at positions similar to those of FIG. 9,with or without paired transducers at each location, preferably without.Accordingly, in one format, one subset of the readers and/or writers areused. In other format, another subset of the readers and/or writers areused.

In a further approach to a multiformat embodiment of FIG. 10, onlywriters in an array compatible with the new format may be present on theouter modules, with the inner module having readers arranged to readboth legacy and new formats. This allows backward compatibility, atleast for retrieving data from legacy tapes.

In a further approach to a multiformat embodiment of FIG. 11, readers inan array compatible with the legacy and new formats may be present onthe outer modules, with the inner module having writers arranged towrite only a new format. This allows backward compatibility, at leastfor retrieving data from legacy tapes.

In a variation on the embodiments of FIG. 10 or 11, such embodiments mayhave a multiformat array as in FIG. 9, the inner array of the modulesmay be adjusted for the top and bottom modules so that 32 of thelocations may be used (either 1-32 or 2-33, leaving the first or lastlocation open), thus eliminating a reader and/or writer from theopposite end of the inner array on each module. In addition, the centermodule (not shown) may have a complete set of 33 transducers in theinner array, meaning that the end channels may be a transducer pair (P)on each side, rather than splitting the transducer pair as in the topand bottom modules. This may result in a reader-writer-reader (RWR) orwriter-reader-writer (WRW) on each inner array channel on the head.

In another approach to the various embodiments, the top and bottommodules may be manufactured with a transducer pair (P) on each end ofthe inner array, with one of the transducers in the pair (P) notconnected or operational, and the other transducer pair (P) beingsimilarly only operational for one of the reader or writer, asappropriate.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of a preferred embodiment shouldnot be limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

What is claimed is:
 1. A magnetic head, comprising: an inner modulecomprising an array of data readers; and first and second outer modulesflanking the inner module and spaced therefrom, thereby defining a gapin a tape bearing surface of the head between the first and innermodules and a gap in the tape bearing surface of the head between thesecond and inner modules, wherein the outer modules are identical, eachouter module comprising an array of data writers, wherein a number ofactive data writers in each outer module is less than a number of activedata readers in the inner module, wherein, for the first outer module,one of the active data writers is aligned with one of the data readerspositioned towards a first end of the inner module array in a directiongenerally parallel to the path of tape travel thereacross, wherein, forthe second outer module, one of the active data writers is aligned withone of the data readers positioned towards a second end of the innermodule array in the direction generally parallel to the path of tapetravel thereacross, wherein, for each module, one of the datatransducers is positioned along a centerline of the array, wherein thecenterline is oriented in a direction perpendicular to a longitudinalaxis of the array.
 2. A magnetic head as recited in claim 1, wherein,for each module, only one servo reader is positioned on each side of thearray.
 3. A magnetic head as recited in claim 2, wherein, for eachmodule, a distance between the servo readers is such that the servoreaders read servo bands on a tape written in a first format and servobands on a tape written in a second format.
 4. A magnetic head asrecited in claim 1, wherein a first subset of the transducers in atleast one of the arrays is operable for reading or writing data in afirst tape format, wherein a second subset of the transducers isoperable for reading or writing data in a second tape format, at leastsome of the transducers being present in both subsets, wherein, for eachmodule, the transducers positioned along the centerline of the arraybelong to only one of the subsets.
 5. A magnetic head as recited inclaim 1, wherein a first subset of the transducers in at least one ofthe arrays is operable for reading or writing data in a first tapeformat, wherein a second subset of the transducers is operable forreading or writing data in a second tape format, at least some of thetransducers being present in both subsets, wherein, for each array, thetransducers in each subset have about the same center to center spacing.6. A magnetic head as recited in claim 1, wherein a first subset of thetransducers in at least one of the arrays is operable for reading orwriting data in a first tape format, wherein a second subset of thetransducers is operable for reading or writing data in a second tapeformat, at least some of the transducers being present in both subsets,wherein, for each array, the transducers in the first subset have adifferent center to center spacing than the transducers in the secondsubset.
 7. A magnetic head as recited in claim 6, wherein, for eachmodule, one of the data transducers is positioned along a centerline ofthe array, wherein the centerline is oriented in a directionperpendicular to a longitudinal axis of the array.
 8. A magnetic head asrecited in claim 6, further comprising, for each module, a pair of servoreaders interleaved with the transducers.
 9. A tape drive system,comprising: a magnetic head as recited in claim 1; a drive mechanism forpassing a magnetic recording tape over the head; and a controller incommunication with the head.
 10. A magnetic head as recited in claim 1,wherein an outer writer of the first module is not aligned with a writerof the second module in an intended direction of tape travelthereacross.
 11. A magnetic head as recited in claim 10, wherein anouter writer of the second module is not aligned with a writer of thefirst module in the intended direction of tape travel.
 12. A magnetichead as recited in claim 1, wherein the inner module also has servoreaders.